In non-scientific use, the term sugar refers to sucrose (also called "table sugar" or "saccharose") — a white crystallinesoliddisaccharide. Humans most commonly use sucrose as their sugar of choice for altering the flavor and properties (such as mouthfeel, preservation, and texture) of beverages and food. Commercially produced table sugar comes either from sugar cane or from sugar beet. Manufacturing and preparing food may involve other sugars, including palm sugar and fructose, generally obtained from corn (maize) or fruit.

In this informal sense, the word "sugar" principally refers to crystalline sugars; but a great many foods exist which principally contain sugar: these generally appear as syrups, or have specific names such as "honey" or "molasses." Many of these comprise mostly sugar; and sugar may dissolve in water to form a syrup.

In a list of ingredients, any word that ends with "ose" will likely denote a sugar. Sometimes such words may also refer to any types of carbohydrates soluble in water.

In culinary terms, the foodstuff known as sugar delivers a primary taste sensation of sweetness. Apart from the many forms of sugar and of sugar-containing foodstuffs, alternative non-sugar-based sweeteners exist, and particularly interest people who have problems with their blood sugar level (such as diabetics) and people who wish to limit their calorie-intake, but while enjoying sweet foods to a greater degree. Both natural and synthetic examples exist with no significant carbohydrate (calorie) content, for instance stevia (a herb) and saccharin (produced from naturally occurring but not necessarily naturally edible substances by inducing appropriate chemical reactions).

Sugar and society

For many years, sugar has been distributed through society and has helped shape the community. One example of this is sugar and its effects with language, such as "give me some sugar" or "you're sweet as sugar." Many more alterations of society have been swayed by Sugar, especially in the southern regions of the earth.

History

Early use of sugar-cane in Asia

Sugar-cane, a tropical grass, probably originated in New Guinea. During prehistoric times its culture spread throughout the Pacific Islands and into India. By 200 BC producers in China had begun to grow it too. Westerners learned of sugar cane in the course of military expeditions to India. Nearchos, one of Alexander the Great's commanders, described it as "a reed that gives honey without bees".

Originally, people chewed the cane raw to extract its sweetness. The process of making sugar by evaporating juice from sugar cane developed in India around 500 BC. In South Asia, the Middle East and China, sugar became a staple of cooking and desserts.

Early refining methods involved grinding or pounding the cane in order to extract the juice, and then boiling down the juice or drying it in the sun to yield sugary solids that resembled gravel. The Sanskrit word for "sugar" (sharkara), also means "gravel". Similarly, the Chinese use the term "gravel sugar" (Traditional Chinese: 砂糖) for table sugar.

The 1390s saw the development of a better press, which doubled the juice obtained from the cane. This permitted economic expansion of sugar plantations to Andalucia and to the Algarve. The 1420s saw sugar-production extended to the Canary Islands, Madeira and the Azores.

In August 1492 Christopher Columbus stopped at Gomera in the Canary Islands, for wine and water, intending to stay only four days. He became romantically involved with the Governor of the island, Beatrice de Bobadilla, and stayed a month. When he finally sailed she gave him cuttings of sugar-cane, which became the first to reach the New World.

The Portuguese took sugar to Brazil. Hans Staden, published in 1555, writes that by 1540 Santa Catalina Island had 800 sugar-mills and that the north coast of Brazil, Demarara and Surinam had another 2000. Approximately 3000 small mills built before 1550 in the New World created an unprecedented demand for cast irongears, levers, axles and other implements. Specialist trades in mold-making and iron-casting developed in Europe due to the expansion of sugar-production. Sugar-mill construction developed technological skills needed for a nascent industrial revolution in the early 17th-century.{

After 1625 the Dutch carried sugar-cane from South America to the Caribbean islands — where it became grown from Barbados to the Virgin Islands. The years 1625 to 1750 saw sugar become worth its weight in gold. Contemporaries often compared the worth of sugar with valuable commodities including musk, pearls, and spices. Prices declined slowly as production became multi-sourced, especially through British colonial policy. Formerly an indulgence of the rich, sugar became increasingly common among the poor. Sugar-production increased in mainland North American colonies, in Cuba, and in Brazil. African slaves became the dominant source of plantation-workers, as they proved resistant to the diseases of malaria and yellow fever. (European indentured servants remained in shorter supply, susceptible to disease and overall forming a less economic investment. European diseases such as smallpox had reduced the numbers of local Native Americans.) But replacement of Native American with African slaves also occurred because of the high death-rates on sugar-plantations. The British West Indies imported almost 4 million slaves, but had only 400,000 Blacks left after slavery ended in the British Empire in 1838.

With the European colonization of the Americas, the Caribbean became the world's largest source of sugar. These islands could supply sugar-cane using slave-labor and produce sugar at prices vastly lower than those of cane-sugar imported from the East. Thus the economies of entire islands such as Guadaloupe and Barbados became based on sugar-production. By 1750 the French colony known as Saint-Domingue (subsequently the independent country of Haiti) became the largest sugar-producer in the world. Jamaica too became a major producer in the 18th century. Sugar-plantations fueled a demand for manpower; between 1701 and 1810 ships brought nearly one million slaves to work in Jamaica and in Barbados.

During the eighteenth century, sugar became enormously popular and the sugar-market went through a series of booms. The heightened demand and production of sugar came about to a large extent due to a great change in the eating habits of many Europeans. For example, they began consuming jams, candy, tea, coffee, cocoa, processed foods, and other sweet victuals in much greater numbers. Reacting to this increasing craze, the islands took advantage of the situation and began producing more sugar. In fact, they produced up to ninety percent of the sugar that the western Europeans consumed. Some islands proved more successful than others when it came to producing the product. And in Barbados and the British Leeward Islands sugar provided 93% and 97% respectively of exports.

Planters later began developing ways to boost production even more. For example, they began using more manure when growing their crops. They also developed more advanced mills and began using better types of sugar-cane. Despite these and other improvements, the price of sugar reached soaring heights, especially during events such as the revolt against the Dutch and the Napoleonic Wars. Sugar remained in high demand, and the islands' planters knew exactly how to take advantage of the situation.

As Europeans established sugar-plantations on the larger Caribbean islands, prices fell, especially in Britain. By the eighteenth century all levels of society had become common consumers of the former luxury product. At first most sugar in Britain went into tea, but later confectionery and chocolates became extremely popular. Many Britons (especially children) also ate jams. Suppliers commonly sold sugar in solid cones and consumers required a sugar nip, a pliers-like tool, to break off pieces.

Sugar-cane quickly exhausts the soil in which it grows, and planters pressed larger islands with fresher soil into production in the nineteenth century. In this century, for example, Cuba rose to become the richest land in the Caribbean (with sugar as its dominant crop) because it formed the only major island land-mass free of mountainous terrain. Instead, nearly three-quarters of its land formed a rolling plain — ideal for planting crops. Cuba also prospered above other islands because Cubans used better methods when harvesting the sugar crops: they adopted modern milling-methods such as water-mills, enclosed furnaces, steam-engines, and vacuum-pans. All these technologies increased productivity.

After the Haïtian Revolution established the independent state of Haiti, sugar production in that country declined and Cuba replaced Saint-Domingue as the world's largest producer.

Long established in Brazil, sugar-production spread to other parts of South America, as well as to newer European colonies in Africa and in the Pacific, where it became especially important in Fiji.

In Colombia, the planting of sugar started very early on, and entrepreneurs imported many African slaves to cultivate the fields. The industrialization of the Colombian industry started in 1901 with the establishment of the first steam-powered sugar mill by Santiago Eder.

Napoleon, cut off from Caribbean imports by a British blockade and at any rate not wanting to fund British merchants, banned imports of sugar in 1813. The beet-sugar industry that emerged in consequence grew, and today sugar-beet provides approximately 30% of world sugar production.

While no longer grown by slaves, sugar from developing countries has an on-going association with workers earning minimal wages and living in extreme poverty.

In the developed countries, the sugar industry relies on machinery, with a low requirement for manpower. A large beet-refinery producing around 1,500 tonnes of sugar a day needs a permanent workforce of about 150 for 24-hour production.

Mechanization

Beginning in the late 18th century, the production of sugar became increasingly mechanized. The steam engine first powered a sugar-mill in Jamaica in 1768, and soon after, steam replaced direct firing as the source of process heat.

In 1813 the British chemist Edward Charles Howard invented a method of refining sugar that involved boiling the cane juice not in an open kettle, but in a closed vessel heated by steam and held under partial vacuum. At reduced pressure, water boils at a lower temperature, and this development both saved fuel and reduced the amount of sugar lost through caramelization. Further gains in fuel-efficiency came from the multiple-effect evaporator, designed by the African-American engineer Norbert Rillieux (perhaps as early as the 1820s, although the first working model dates from 1845). This system consisted of a series of vacuum pans, each held at a lower pressure than the previous one. The vapors from each pan served to heat the next, with minimal heat wasted. Today, many industries use multiple-effect evaporators for evaporating water.

The process of separating sugar from molasses also received mechanical attention: David Weston first applied the centrifuge to this task in Hawaii in 1852.

Etymology

The English word "sugar" originates from the Arabic and Persian word shakar.[1] It came to English by way of French, Spanish and/or Italian, which derived their word for sugar from the Arabic and Persian shakar (whence the Portuguese word açúcar, the Spanish word azúcar, the Italian word zucchero, the Old French word zuchre and the contemporary French word sucre). (Compare the OED.) The Greek word for "sugar" is zahari, which means "sugar" or "pebble". Note that the English word jaggery (meaning "coarse brown Indian sugar") has similar ultimate etymological origins (presumably in Sanskrit).

Sugar as food

Originally a luxury, sugar eventually became sufficiently cheap and common to influence standard cuisine. Britain and the Caribbean islands have cuisines where the use of sugar become particularly prominent.

Concerns of vegetarians and vegans

The sugar-refining industry often uses bone char (calcinated animal bones) for decolorizing. This concerns vegans and vegetarians; about a quarter of the sugar in the U.S. gets processed using bone char as a filter and the rest gets processed with activated carbon. As bone char does not get into the sugar, the relevant authorities consider sugar processed this way as parve/kosher.

Vegetarians and vegans may also object to the impact that the burning of the cane fields (a common part of the harvesting practice) has on insects, rats, snakes, and other life residing in the fields.[2]
The killing of such species parallels the killing of bees in the course of the production of honey, another sweetener that vegans usually avoid.

Sugar and health

Whereas historically rotting teeth once seemed the most prominent health-hazard from the use of sugar, first the growth in the usage of rum (a sugar-cane derivative) and then concerns about type 2 diabetes and obesity have gradually come into prominence.

Tooth-decay

Tooth-decay, arguably the most prominent health hazard associated with the use of sugar, can damage teeth in many ways. Bacteria in the mouth metabolize sugar into various acids. When the pH at the surface of the tooth drops below 5.5 (known as the "critical pH"), the acids start dissolving tooth-enamel. This results in decay of the tooth.

Diabetes

Diabetes, a disease that causes the body to metabolize sugar poorly, occurs when either:

the body's cells ignore insulin, a chemical that allows the metabolizing of sugar (Type 2 diabetes)

the body attacks the cells producing the insulin (Type 1 diabetes)

When glucose builds up in the bloodstream, it can cause two problems:

in the short term, cells become starved for energy because they do not have access to the glucose

in the long term, frequent glucose build-up can damage many of the body's organs, including the eyes, kidneys, nerves and/or heart

However, while sugars may adversely affect those with diabetes, science has not proven that sugars cause diabetes.

Obesity

In the United States of America, a scientific/health debate has startedover the causes of a steep rise in obesity in the general population — and one view posits increased consumption of carbohydrates in recent decades as a major factor.[3]

Obesity can result from a number of factors including:

an increased intake of energy-dense foods — high in fat and sugars but low in vitamins, minerals and other micronutrients; and

United Nations nutritional advice

In 2003, four United Nations agencies, (including the World Health Organization (WHO) and the Food and Agriculture Organization (FAO)) commissioned a report compiled by a panel of 30 international experts. The panel stated that the total of free sugars (all monosaccharides and disaccharides added to foods by manufacturers, cooks or consumers, plus sugars naturally present in honey, syrups and fruit juices) should not account for more than 10% of the energy intake of a healthy diet, while carbohydrates in total should represent between 55% and 75% of the energy-intake (table 6, page 56 of the WHO Technical Report Series 916, Diet, Nutrition and the Prevention of Chronic Diseases: see http://www.fao.org/docrep/005/AC911E/ac911e07.htm#bm07.1.3 ).

Sugar producers’ nutritional advice

In contradistinction to the United Nations report, the Sugar Association of the United States of America insists that other evidence indicates that a quarter of human food and drink intake can safely consist of sugar.

Debate on extrinsic sugar

Argument continues as to the value of extrinsic sugar (sugar added to food) compared to that of intrinsic sugar (sugars - seldom sucrose - naturally present in food). Adding sugar to food particularly enhances taste, but has drawbacks of boosting calories, among other negative effects on health and physiology.

In the United States of America, sugar has become increasingly evident in food products, as more food-manufacturers add sugar or high-fructose corn-syrup to a wide variety of consumables. Candy-bars, soft drinks, chips, snacks, fruit-juice, peanut-butter, soups, ice-cream, jams, jellies, yogurt, and many breads have added sugars. Five Alive, for example, portrayed by its suppliers as "all natural" and featuring pictures of five different types of fruit on its label, comprises only 41% fruit juice, having high-fructose corn-syrup as its prime ingredient.

Many doctors argue that health authorities should classify sugar and high-fructose corn-syrup as food additives.[5]
Some go so far as to call refined sugar a poison.[6]

The anthropologist and dentist Weston A. Price, writing in 1939,[7]
correlated the use of refined sugar (and refined grains) with malnutrition in pregnant women, malformation of the palate and jaw in their children, followed by cramping of teeth in adolescence (leading to crooked teeth and the removal of wisdom teeth molars). Price correlated other ailments and the impaired function of the pituitary or master gland with consumption of refined sugar, as well as rates of infant mortality, subnormal intelligence, delinquency, and incarceration. He also correlated the underdevelopment of the pelvis, which in women would lead to complications (pain, death, etc.) in childbirth.

Virtually all of these symptoms became the norm in modern populations consuming typical amounts of refined sugar and other "modern foods of commerce". Besides the rotting of teeth, interruptible or resumable merely by removing or re-introducing white sugar into a diet, the correlations with consumption of refined sugar may relate less to the consumption of refined sugar itself than to the absence of the consumption of "nourishment", a category in which Price did not include refined sugar.

Nutrition

Sugar-cane in its natural form provides a rich source of vitamins and minerals, but refined sugar lacks many nutrients.

Sugar and hyperactivity

Sugar (not only sucrose, but also other varieties such as glucose) may cause some children to become hyperactive — giving rise to the terms "sugar high", "sugar rush" and "sugar buzz". Recent studies financed by the sugar-industry found that in a party situation all children became very active after only some had consumed sugar, thus demonstrating the lack of a direct link between individual consumption of sugar and individual levels of hyperactivity in that party context, even when the researchers focused on children with a presumed "sugar-sensitivity". If sugar-industry researchers believe sugar does not contribute to hyperactivity, or if parents and teachers believe in the possibility of a sugar-high, their respective biases may cause them to perceive children accordingly after consumption of sweets and sugary beverages through observer-bias. (Note that the experiments did not take place in the context of a control-group following a base diet-level matching the recommendation of the WHO/FAO (stated above) to avoid the impacts of added extrinsic sugars cited above, nor in a controlled setting — and so could not give credible results.)

Some commentators believe that children and adults show the hyperactive effects of sugar equally. On average, Americans eat or drink approximately five pounds of sugar a month.[8]

Production

Table sugar (sucrose) comes from plant sources. Two important sugar crops predominate: sugarcane (Saccharum spp.) and sugar beets (Beta vulgaris), in which sugar can account for 12% to 20% of the plant's dry weight. Some minor commercial sugar crops include the date palm (Phoenix dactylifera), sorghum (Sorghum vulgare), and the sugar maple (Acer saccharum). In the financial year 2001/2002, worldwide production of sugar amounted to 134.1 million tonnes.

The first production of sugar from sugar-cane took place in India. Alexander the Great's companions reported seeing "honey produced without the intervention of bees" and it remained exotic in Europe until the Arabs started cultivating it in Sicily and Spain. Only after the Crusades did it begin to rival honey as a sweetener in Europe. The Spanish began cultivating sugar-cane in the West Indies in 1506 (and in Cuba in 1523). The Portuguese first cultivated sugar-cane in Brazil in 1532.

Most cane-sugar comes from countries with warm climates, such as Brazil, India, China, Thailand, Mexico and Australia, the five top sugar producing countries in the world.[9] Brazil overshadows most countries with roughly 30 million tonnes of cane sugar produced in 2006, while India produced 21 million, China 11 million, and Thailand and Mexico at roughly 5 million. Viewed by region, Asia is the world-leader in cane-sugar production with large contributions from China, India and Thailand and other countries combining to account for 40% of global production in 2006. South America comes in second place with 32% of global production, Africa and Central America both at 8% and Australia at 5%. The United States, the Caribbean and Europe make up the remainder with roughly 3% each.[10]

Beet-sugar comes from regions with cooler climates: northwest and eastern Europe, northern Japan, plus some areas in the United States (including California). In the northern hemisphere, the beet-growing season ends with the start of harvesting around September. Harvesting and processing continues until March in some cases. The availability of processing-plant capacity, and the weather both influence the duration of harvesting and processing - the industry can lay up harvested beet until processed, but frost-damaged beet becomes effectively unprocessable.

The European Union (EU) has become the world's second-largest sugar exporter. The Common Agricultural Policy of the EU sets maximum quotas for members' production to match supply and demand, and a price. Europe exports excess production quota (approximately 5 million tonnes in 2003). Part of this, "quota" sugar, gets subsidised from industry levies, the remainder (approximately half) sells as "C quota" sugar at market prices without subsidy. These subsidies and a high import tariff make it difficult for other countries to export to the EU states, or to compete with the Europeans on world markets.

The United States sets high sugar prices to support its producers, with the effect that many former consumers of sugar have switched to corn syrup (beverage-manufacturers) or moved out of the country (candy-makers).

The cheap prices of glucose syrups produced from wheat and corn (maize) threaten the traditional sugar market. In combination with artificial sweeteners, drink manufacturers can produce very low-cost products.

Cane

Since the 6th century BC cane-sugar producers have crushed the harvested vegetable material from sugar-cane in order to collect and filter the juice. They then treat the liquid (often with lime (calcium oxide)) to remove impurities and then neutralize it. Boiling the juice then allows the sediment to settle to the bottom for dredging out, while the scum rises to the surface for skimming off. In cooling, the liquid crystallizes, usually in the process of stirring, to produce sugar crystals. Centrifuges usually remove the uncrystallized syrup. The producers can then either sell the resultant sugar, as is, for use; or process it further to produce lighter grades. This processing may take place in another factory in another country.

Beet

Beet-sugar producers slice the washed beets, then extract the sugar with hot water in a "diffuser". An alkaline solution ("milk of lime" and carbon dioxide from the lime kiln) then serves to precipitate impurities (see carbonatation). After filtration, evaporation concentrates the juice to a content of about 70% solids, and controlled crystallisation extracts the sugar. A centrifuge removes the sugar crystals from the liquid, which gets recycled in the crystalliser stages. When economic constraints prevent the removal of more sugar, the manufacturer discards the remaining liquid, now known as molasses.

Sieving the resultant white sugar produces different grades for selling.

Cane versus beet

Little perceptible difference exists between sugar produced from beet and that from cane. Tests can distinguish the two, and some tests aim to detect fraudulent abuse of EU subsidies or to aid in the detection of adulterated fruit-juice.

The production of sugar results in residues which differ substantially depending on the raw materials used and on the place of production. While cooks often use cane molasses in food, humans find molasses from sugar beet unpalatable, and it therefore ends up mostly as industrial fermentation feedstock, or as animal-feed. Once dried, either type of molasses can serve as fuel for burning.

Culinary sugars

So-called raw sugars comprise yellow to brown sugars made by clarifying the source syrup by boiling and drying with heat, until it becomes a crystalline solid, with minimal chemical processing. Raw beet sugars result from the processing of sugar-beet juice, but only as intermediates en route to white sugar. Types of raw sugar include demerara, muscovado, and turbinado. Mauritius and Malawi export significant quantities of such specialty sugars. Manufacturers sometimes prepare raw sugar as loaves rather than as a crystalline powder, by pouring sugar and molasses together into molds and allowing the mixture to dry. This results in sugar-cakes or loaves, called jaggery or gur in India, pingbian tang in China, and panela, panocha, pile, piloncillo and pão-de-açúcar in various parts of Latin America. In South America, truly raw sugar, unheated and made from sugar-cane grown on farms, does not have a large market-share.

Mill white sugar, also called plantation white, crystal sugar, or superior sugar, consists of raw sugar where the production process does not remove colored impurities, but rather bleaches them white by exposure to sulfur dioxide. Though the most common form of sugar in sugarcane-growing areas, this product does not store or ship well; after a few weeks, its impurities tend to promote discoloration and clumping.

Blanco directo, a white sugar common in India and other south Asian countries, comes from precipitating many impurities out of the cane juice by using phosphatation — a treatment with phosphoric acid and calcium hydroxide similar to the carbonatation technique used in beet-sugar refining. In terms of sucrose purity, blanco directo is more pure than mill white, but less pure than white refined sugar.

White refined sugar has become the most common form of sugar in North America as well as in Europe. Refined sugar can be made by dissolving raw sugar and purifying it with a phosphoric acid method similar to that used for blanco directo, a carbonatation process involving calcium hydroxide and carbon dioxide, or by various filtration strategies. It is then further purified by filtration through a bed of activated carbon or bone char depending on where the processing takes place. Beet sugar refineries produce refined white sugar directly without an intermediate raw stage. White refined sugar is typically sold as granulated sugar, which has been dried to prevent clumping.

Granulated sugar comes in various crystal sizes — for home and industrial use — depending on the application:

Coarse-grained sugars, such as sanding sugar (nibbed sugar or sugar nibs) find favor for decorating cookies/biscuits and other desserts.

Normal granulated sugars for table use: typically they have a grain size about 0.5 mm across

Retailers also sell sugar cubes or lumps for convenient consumption of a standardised amount. Suppliers of sugar-cubes make them by mixing sugar crystals with sugar syrup. Jakub Kryštof Rad invented sugar-cubes in 1841.

Brown sugars come from the late stages of sugar refining, when sugar forms fine crystals with significant molasses-content, or from coating white refined sugar with a cane molasses syrup. Their color and taste become stronger with increasing molasses-content, as do their moisture-retaining properties. Brown sugars also tend to harden if exposed to the atmosphere, although proper handling can reverse this.

The World Health Organisation and the Food and Agriculture Organization of the United Nations expert report (WHO Technical Report Series 916 Diet, Nutrition and the Prevention of Chronic Diseases) defines free sugars as all monosaccharides and disaccharides added to foods by the manufacturer, cook or consumer, plus sugars naturally present in honey, syrups and fruit-juices. This includes all the sugars referred to above. The term distinguishes these forms from all other culinary sugars added in their natural form with no refining at all.

Natural sugars comprise all completely unrefined sugars: effectively all sugars not defined as free sugars. The WHO Technical Report Series 916 Diet, Nutrition and the Prevention of Chronic Diseases approves only natural sugars as carbohydrates for unrestricted consumption. Natural sugars come in fruit, grains and vegetables in their natural or cooked form.

Chemistry

Sucrose: a disaccharide of glucose (left) and fructose (right), important molecules in the body.

Biochemists regard sugars as relatively simple carbohydrates. Sugars include monosaccharides, disaccharides, trisaccharides and the oligosaccharides - containing 1, 2, 3, and 4 or more monosaccharide units respectively. Sugars contain either aldehyde groups (-CHO) or ketone groups (C=O), where there are carbon-oxygen double bonds, making the sugars reactive. Most simple sugars (monosaccharides) conform to (CH2O)n where n is between 3 and 7. A notable exception, deoxyribose, as its name suggests, has a "missing" oxygen atom. All saccharides with more than one ring in their structure result from two or more monosaccharides joined by glycosidic bonds with the resultant loss of a molecule of water (H2O) per bond.

As well as using classifications based on their reactive group, chemists may also subdivide sugars according to the number of carbons they contain. Derivatives of trioses (C3H6O3) are intermediates in glycolysis. Pentoses (5-carbon sugars) include ribose and deoxyribose, which form part of nucleic acids. Ribose also forms a component of several chemicals that have importance in the metabolic process, including NADH and ATP. Hexoses (6-carbon sugars) include glucose, a universal substrate for the production of energy in the form of ATP. Through photosynthesis plants produce glucose, which has the formula C6H12O6, and then convert it for storage as an energy-reserve in the form of other carbohydrates such as starch, or (as in cane and beet) as sucrose (table sugar). The chemical formula for sucrose is C12H22O11.

Many pentoses and hexoses can form ring structures. In these closed-chain forms, the aldehyde or ketone group remains unfree, so many of the reactions typical of these groups cannot occur. Glucose in solution exists mostly in the ring form at equilibrium, with less than 0.1% of the molecules in the open-chain form.

Monosaccharides in a closed-chain form can form glycosidic bonds with other monosaccharides, creating disaccharides (such as sucrose) and polysaccharides (such as starch). Enzymes must hydrolyse or otherwise break these glycosidic bonds before such compounds will be metabolised. After digestion and absorption. the principal monosaccharides present in the blood and internal tissues include glucose, fructose, and galactose.

The prefix "glyco-" indicates the presence of a sugar in an otherwise non-carbohydrate substance. Note for example glycoproteins, proteins which are connected to one or more sugars.

Monosaccharides include fructose, glucose, galactose and mannose. Disaccharides occur most commonly as sucrose (cane or beet sugar - made from one glucose and one fructose), lactose (milk sugar - made from one glucose and one galactose) and maltose (made of two glucoses). These disaccharides have the formula C12H22O11.

Hydrolysis can convert sucrose into a syrup of fructose and glucose, producing invert sugar. This resulting syrup, sweeter than the original sucrose, has uses in making confections because it does not crystallize as easily and thus produces a smoother finished product.

Measuring sugar

Dissolved sugar content

Scientists use degrees Brix (symbol °Bx), introduced by Antoine Brix, as units of measurement of the mass ratio of dissolved substance to water in a liquid. A 25 °Bx sucrose solution has 25 grams of sucrose per 100 grams of liquid; or, to put it another way, 25 grams of sucrose sugar and 75 grams of water exist in the 100 grams of solution.

An infrared Brix sensor measures the vibrational frequency of the sugar molecules, giving a Brix degrees measurement. This does not equate to Brix degrees from a density or refractive index measurement because it will specifically measure dissolved sugar concentration instead of all dissolved solids. When using a refractometer, one should report the result as "refractometric dried substance" (RDS). One might speak of a liquid as having 20 °Bx RDS. This refers to a measure of percent by weight of total dried solids and, although not technically the same as Brix degrees determined through an infrared method, renders an accurate measurement of sucrose content, since sucrose in fact forms the majority of dried solids. The advent of in-line infrared Brix measurement sensors has made measuring the amount of dissolved sugar in products economical using a direct measurement.

Sugar purity

Technicians usually measure the purity of sugar, i.e. the sucrose content, by polarimetry — the measurement of the rotation of plane-polarized light by a solution of sugar.

Sugar economics

Historically one of the most widely-traded commodities in the world, sugar accounts for around 2% of the global dry cargo market. International sugar prices show great volatility, ranging from around 3 to over 60 cents per pound in the past 50 years. Of the world's 180-odd countries, around 100 produce sugar from beet or cane, a few more refine raw sugar to produce white sugar, and all countries consume sugar. Consumption of sugar ranges from around 3 kilograms per person per annum in Ethiopia to around 40 kg/person/yr in Belgium. Consumption per capita rises with income per capita until it reaches a plateau of around 35kg per person per year in middle-income countries.

Many countries subsidize sugar-production heavily. The European Union, the United States, Japan and many developing countries subsidize domestic production and maintain high tariffs on imports. Sugar prices in these countries have often exceeded prices on the international market by up to three times; today, with world market sugar futures prices currently strong, such prices typically exceed world prices by two times.

Within international trade bodies, especially in the World Trade Organization, the "G20" countries led by Brazil have long argued that because these sugar markets essentially exclude cane-sugar imports, the G20 sugar-producers receive lower prices than they would under free trade. While both the European Union and United States maintain trade agreements whereby certain developing and less-developed countries (LDCs) can sell certain quantities of sugar into their markets, free of the usual import tariffs, countries outside these preferred trade régimes have complained that these arrangements violate the "most favoured nation" principle of international trade.

In 2004, the WTO sided with a group of cane-sugar exporting nations (led by Brazil and Australia) and ruled the EU sugar-régime and the accompanying ACP-EU Sugar Protocol (whereby a group of African, Caribbean, and Pacific countries receive preferential access to the European sugar market) illegal.[12] In response to this and to other rulings of the WTO, and owing to internal pressures on the EU sugar-régime, the European Commission proposed on 22 June 2005 a radical reform of the EU sugar-régime, cutting prices by 39% and eliminating all EU sugar exports.[13]
The African, Caribbean, Pacific and least developed country sugar-exporters reacted with dismay to the EU sugar proposals,[14]. On 25 November 2005 the Council of the EU agreed to cut EU sugar-prices by 36% as from 2009. It now seems[15] that the U.S. Sugar Program could become the next target for reform. However, some commentators expect heavy lobbying from the U.S. sugar-industry, which donated $2.7 million to House and Senate incumbents in the 2006 election, more than any other group of US food growers.[16] Especially prominent in this group are The Fanjul Brothers, sugar barons who are the single largest individual contributors of soft money to both the Democratic and Republican parties in the political system of the United States of America.[17][18]

Small quantities of sugar, especially specialty grades of sugar, reach the market as 'fair trade' commodities; the fair-trade system produces and sells these products with the understanding that a larger-than-usual fraction of the revenue will support small farmers in the developing world. However, whilst the Fairtrade Foundation offers a premium of USD 60.00 per tonne to small farmers for sugar branded as "Fairtrade",[19]
government schemes such the U.S. Sugar Program and the ACP Sugar Protocol offer premiums of around USD 400.00 per tonne above world market prices. However, the EU announced on 14 September 2007 that it would denounce the ACP Sugar Protocol with effect from 1 October 2009.[20][21]

The Sugar Association has launched a campaign to promote sugar over artificial substitutes. The Association now aggressively challenges many common beliefs regarding negative side effects of sugar consumption. The campaign aired a high-profile television-commercial during the 2007 Prime Time Emmy Awards on FOX Television. The Sugar Association uses the trademark tagline "Sugar: sweet by nature."[22]